code: def test_lookback(self):
      buffer = BufferWithInfiniteLookback(data=[0, 1, 2, 3], lookback=2)
      self.assertTrue(len(buffer), 2)
      data_no_lookback = buffer.get()
      check(data_no_lookback, [2, 3])
      buffer.append(4)
      self.assertTrue(len(buffer), 3)
      buffer.append(5)
      self.assertTrue(len(buffer), 4)
      data_no_lookback = buffer.get()
      check(data_no_lookback, [2, 3, 4, 5])
      buffer.pop()
      self.assertTrue(len(buffer), 3)
      data_no_lookback = buffer.get()
      check(data_no_lookback, [2, 3, 4])
  
file_path: ray/rllib/env/tests/test_lookback_buffer.py
imports: import unittest
  import gymnasium
  import numpy
  from ray.rllib.env.utils import BufferWithInfiniteLookback
  from ray.rllib.utils.spaces.space_utils import batch, get_dummy_batch_for_space
  from ray.rllib.utils.test_utils import check
label_desc: Use image node_id 3 for calling the TestBufferWithInfiniteLookback obj's underlying member method code with example usage: obj.test_lookback() without return types